Removes the maintenance role
Removes assignee as a concept
Role may only be admin or staff
ROLES defines valid roles
Removes the assignee_id column
Removes the assigned_at column too
Adds assigned as a status
Merge remote-tracking branch 'origin/master' into fire-maintenance-role

Conflicts:
	app/models/service_request.rb
	app/views/service_requests/_service_request.json.jbuilder
Merge pull request #82 from alindeman/fire-maintenance-role

Removes the 'maintenance' role